RFR: 8366328: G1: Crash on reading os::thread_cpu_time

[David Holmes]

On Wed, 10 Sep 2025 07:57:10 GMT, Ivan Walulya <iwalulya at openjdk.org> wrote:

> > Can you not use VMThread::is_terminated() to check for shutdown?
> 
> `before_exit(thread)` happens before `VMThread::wait_for_vm_thread_exit();` which sets the `_is_terminated`, so it too late since we terminate the concurrent GC threads at `before_exit`.

Okay, I'm a little surprised we don't have a pre-existing global indicator of the fact we have started shutting down via `before_exit`. Makes me think though that this G1 specific flag should be at the level of `heap()` or even `Universe`.

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PR Comment: https://git.openjdk.org/jdk/pull/27087#issuecomment-3277045064